Supposedly at his trial the future canonized saint, Thomas More, justifying his silence in the matter of his opinion on King Henry's divorce said "qui tacit consentire videtur"...translated fairly well in the movie A Man For All Seasons, "silence betokens consent". To this, his accuser, Oliver Cromwell, said in rebuttal that silence indicates many things, including treason, and that, very strongly.

Silence speaks loudly....

Concerning intelligent (sentient) life in the universe, if the Drake equation is anywhere near correct, there should be millions, if not billions of sentient civilizations throughout space. On average, these should be about two and a half billion years advanced of us technologically, with the same amount of time to have disseminated their communications throughout the universe and traveled throughout the universe.

But, we have no verifiable evidence of their presence or existence. We don't even have visual or radio or sensory evidence of their having used/mis-used/played-with awesome energies of which their advanced technologies should have given signs (e.g. stars obliterating, stars blinking out, star like flashes or glares, etc.).

In my gut (meaning, I haven't thought this through with either rigourous logic or serious intellectual research) I feel this silence betokens either there is no intelligent/sentient life elsewhere, or that the geometries of scale in the universe are so large and the limitations of physics so severe even they can't overcome them.

The Drake equation does not say how many civilizations there should be, or how old they should be. It sets up a bunch of variables that should affect the final number. Depending on what you plug in for those variables, the number can vary from billions to none.

As for things like stars obliterating, we see lots of those. We call them supernovas, gamma ray bursts, etc. We just don't think they are due to a civilization. But if you postulate a civilization wanting to use tremendous amounts of energy on the order of a GRB, it would look the same to us at this distance.

I am on the side of the scale being the issue. I think there is probably something out there, but it may be so far away that we will never meet.

Me too.That scale is in both space and time. Just because we have done some extremely rudementary space "travel", we assume I think too easily that some "more advanced" life forms must be doing alot of stuff.

Speaking about life "similar to our own":

Given our own experience, and what the Hubble ,inter alia, has revealed of the violent nature of the cosmos, I would not be at all surprised if few sentient forms make it off the birth planet, much less even establish a successful, large, breeding population in their own solar system.

The only reason we went to the moon when we did was pseudospeciation (cold war). I doubt very much (at least right now) that we will spread out through our own system. Any form similar to our own would be battling against a bunch of biologically predispositioned behaviors to do so.

I am not sure about the 2.5 billion years old civilizations.There must be a requirement for a high metallicity star, like or sun, to promote life, and that means probably a 2nd or third generation star. Also this star must be in the outer galaxy zone because the center is too 'irradiated'. The requirement for high metallicity and fissile isotopes will help the planet to evade the initial 'faint sun' phase by internal warming. Were stars like our sun available in the outer galaxy zone 7 or 8 billion years ago? if not, then there is no such 2.5 billion old civilization possible, but given the rate of technical advancement, a civilization just ahead of 100 years might do the job as well.Also, the idea of random search for life is dead IMO, we are not blind at all, we can't touch, but we can see. I opened a topic on interferomtry a while ago at

If this civilization is just ahead 100 years of us technically, they also figured how to detect exoplanets and therefore 'they' know where we are and that Earth has water oxygen and greenish patches. Even at 200 light years from us, they could possibly see some lights in the dark hemisphere. From there, what would they do, or what would we do?

I'm pretty sure the Drake equation (Walter Drake, educated at Cornell, NRO, 1961 came up with the equation) does estimate the number of technologically advanced civilizations.

Am I incorrect on this? or does my statement need to be qualified in some way?

As to how technologically advanced they are, that came from somewhere else which I forget. It might have been my own crude math, or it may have come from my teacher, Myron **** o.s.c. who studied under Sagan. I forget the numbers on which is based the 2.5 billion superiority of 99%, but I remember it has something to do with the fact the core is made up of generation 1 and the arms of generation 2 and our solar system is at the young end of the technological growth spurt.

I would really appreciate someone telling me/the rest of us what the estimates are on the average age of superiority and percent of technological systems in advance of us.

The equation is:
N = R * fp * ne * *fl * * fc * L
where
R = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

We have rough estimates for R and fp. We don't have any idea about the others. Depending on what you plug in, you can get whatever result you want. To play with the possibilities, there is an online calculator here.

I think, Jarad, you and I agree again but we are having a problem because you are using language as a trained statistician would and I use as a trained philosopher would.

By estimate, I understand that a "correct" answer is not being given in the sense that 4 is the correct answer for "what is 2 plus 2?" I almost equate the word "estimate" with "educated guess". In philosophy we call this a conclusion based on a set of premises, a whole bunch of assumptions having been made and agreed to for the sake of argument any one of which might be wrong, thus calling into question any "estimate" given. That's how I understand it.

I think Drake thought he was giving an "estimate" in this sense, and I think Drake thought his estimate was valuable in terms of adding to a philosophical dialogue intent on guiding scientific investigation.

Or is it, perhaps, you are saying "yes, Drake understood himself to be generating an "estimate" in this sense, but he was incorrect as to what the "estimate" would generate?

Furthermore SETI is set up in such a manner that we could be living in a galactic metropolis and SETI would never even pick it up.

I find it odd when people talk of "the silence" as if our current level of detection capability is the defacto top of the line.

For example, for seti to detect a signal it has to be a signal directly aimed for Earth, in a given frequency.

We can't pick up just normal radio traffic. For example, if an intelligent civilization orbitting a planet around Alpha Centauri AB had television stations that functions like ours do, current SETI would not detect the signals.

We have no technology as of yet that can detect interstellar radio leakage.

I think there is only one advanced civilization on every one in a hundred galaxies, evolving so wide apart that any chance of the two communicating and visiting each other is beyond the realms of what could be possibly allowed by technology and the laws of science. It always sparks our imagination when we hear from a certain Michio Kaku and Neil DeGrasse Tyson, who speak wonderful things about time travel, faster than speed of light, aliens turning off/on a star etc. There has been no evidence of aliens and UFOs, so lets just treat this subject as scientific fantasy than a scientific reality.

#1, of course. With our current technology the type of signals we are capable of detecting is very few. It has to be a narrow beam signal aimed directly at the planet, and we have to be listening to it during it's duration.

Our technology hasn't advanced far enough yet to do much more.

Aliens on a planet around Alpha Centauri AB could be using TV/Radio just like we are and with our current level of technology we are unable to detect such leakage. We'd only know they were there if they deliberately beamed a signal at Earth in a certain frequency range and only if we are listening at the time.

We agree we aren't hearing (do not currently possess) information/signals/whatever indicating the presence of extra-terrestrial sentient life?

It would be more accurate to say that we have not identified anything as transmissions from extra-terrestrial sentient life. (That is, it's possible that we already received signals but didn't recognize them as such.)

1. We aren't listening correctly (i.e. at an inferior technological level or level of inferior political willingness)

2. The geometries of scale and limits of physical reality are making any contact there might be difficult.

3. We're alone.

There is no evidence to support or eliminate any of the possibilities. And we never will. (Unless we actually receive such a signal and thus invalidate the question.)

Of the species of advanced intelligence that discovered the use of the radio spectrum for communication purposes, they do not use it permanently, moving on to other things.

Species of advanced intelligence who develop technological solutions to problems often exhaust the resources of their home planet before becoming spacefaring, then simplify to a pre-tech level.

Species of advanced intelligence who develop technological solutions to problems often destroy themselves.

One i have wondered about. If we did not have an "easy" first target (the moon) circling us, how fast would be have done the little space stuff we have done to date? The moon has taught us alot in the last couple thousand years.

You wrote, "One i have wondered about. If we did not have an "easy" first target (the moon) circling us, how fast would be have done the little space stuff we have done to date? The moon has taught us alot in the last couple thousand years. "

I think your point is very well made. I have two comments about it.

I think it was in a discussion I had over lunch with the astronaut Story Musgrave. The statement was made that going into space, surviving in space, working in space is proving much more difficult than we first imagined.

It may be prohibitively more difficult.

The second thought. Somewhere, I heard that the primary feature on the unseen side of the moon is some huge multi-ring crater that looks like an eyeball. It has been suggested, if this had been the side presenting itself facing in our direction of view, this would have had tremendous ramifications for everything from our religions to mythology to inhibitions or inducements to scientific investigation.

Back to the original question; as I said to Marco, he is correct we can't know which explanation is correct, but at a gut level, would you be willing to say which of the explanations you feel is most correct in explaining the silence?

I heard that the primary feature on the unseen side of the moon is some huge multi-ring crater that looks like an eyeball. It has been suggested, if this had been the side presenting itself facing in our direction of view, this would have had tremendous ramifications for everything from our religions to mythology to inhibitions or inducements to scientific investigation.

Yes. I have also wondered about that.

..at a gut level, would you be willing to say which of the explanations you feel is most correct in explaining the silence?

Silence may mean only that some other bodies in the solar system and beyond harbor lifeforms which can't communicate beyond their immediate surroundings. For sure, anyone listening from a point 126 LY or more away from Earth would still be waiting to detect the first feeble wireless signals our species (one of millions on our planet) was able to propagate.